Techopedia explains Spaghetti Diagram

In a spaghetti diagram, drawn lines represent the movement of people, goods or data through various components of the system. Spaghetti diagrams can be set up to show the relative proximity of different parts of a workspace or otherwise help viewers to understand the processes that things go through to get to their destinations.

One of the major benefits of a spaghetti diagram is that viewers can see how items move, physically or conceptually, within the system. They can observe these complex relationships to try to make them more efficient or to cut down on waste. For example, someone creating a spaghetti diagram might draw rectangles and circles that represent actual workstations in a manufacturing process. The presenter draws a line wherever a product or material moves between different workstations. In many cases, changing the process can make these workflows simpler and boost productivity.